Method of manufacturing ferrule assemblies

ABSTRACT

A method of manufacturing a ferrule assembly. The method including first and second polishing operations. The first polishing operation including polishing only the end face of a ferrule of an assembly. The second polishing operation including polishing only the optical fiber of the assembly.

FIELD OF THE INVENTION

This disclosure relates to methods and devices for use in thetelecommunications industry. More specifically, this disclosure relatesto methods and devices for manufacturing multi-fiber ferrule assemblieshaving polished optical fibers.

BACKGROUND OF THE INVENTION

A multi-fiber ferrule assembly generally includes a ferrule and a numberof optical fibers that are held by the ferrule. Multi-fiber ferruleassemblies are utilized in fiber optic connectors. In use, fiber opticconnectors interconnect to one another for the transmission ortransference of signals. In order to effectively interconnect or matefiber optic connectors, the ends of the optical fibers of the connectorsare generally brought into direct contact with one another. The opticalfibers can project outward from the front face of the ferrule assembliesto aid in establishing the direct contact between the fibers of theconnectors.

In conventional manufacturing processes, the optical fibers of themulti-fiber ferrule assemblies are first polished or ground flush withthe front face of the ferrules. The front faces of the ferrules are thensubsequently ground or polished away from the optical fibers so that thefibers extend a distance beyond the front face. In some processes, thisstep involves using slurry or flock film material to polish both theoptical fiber and the ferrule. Because the ferrule material (e.g.,plastic) is softer than the optical fiber, the front face of the ferrulewears or grinds away more quickly than the optical fiber. The opticalfiber accordingly projects outward from the front face of the ferrule.

As the ferrule material wears away or recedes, the height of the opticalfiber increases, and more and more polishing force is applied to theoptical fiber than to the front face of ferrule. The increasingpolishing force can accelerate the rate at which material from theoptical fiber is removed; accordingly, the distance differential betweenthe optical fiber height and the front face is limited. Suchconventionally manufacture ferrule assemblies typically have opticalfibers that extend a distance of 3 micrometers or less beyond the frontface of the ferrule.

In some applications, the distance of 3 micrometers or less is notsufficient to establish direct contact between fiber optic connectors,thereby resulting in poor signal transmission. In general, conventionalmethods for manufacturing multi-fiber ferrule assemblies can beimproved.

SUMMARY OF THE INVENTION

The present disclosure relates to methods of manufacturing ferruleassemblies. The method includes pre-polishing blank ferrules in a firstpolishing operation and polishing optical fibers of loaded ferrules in asecond polishing operation. In one variation of the method, opticalfibers of a first group of pre-polished ferrules are polishedsimultaneously with end faces of a second group of un-polished ferrules.In another variation of the method, optical fibers of pre-polishedferrules are polished on a tool having a spacer.

In either variation of the present method, the optical fibers arepolished to a desired fiber height without removing material from theassociated ferrule. That is, two polishing operations are utilized tomanufacture the multi-fiber ferrule assembly: a first polishingoperation wherein only the ferrule is polished, and a second operationwherein only the optical fiber is polished. As will be described ingreater detail, this process produces ferrule assemblies having anincreased fiber height. Features of the variations of the present methodalso include providing an indication of the fiber height duringpolishing operations.

A variety of examples of desirable product features or methods are setforth in part in the description that follows, and in part will beapparent from the description, or may be learned by practicing variousaspects of the disclosure. The aspects of the disclosure may relate toindividual features as well as combinations of features. It is to beunderstood that both the foregoing general description and the followingdetailed description are explanatory only, and are not restrictive ofthe claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a (front view) schematic representation of a multi-fiberferrule assembly manufactured in accordance with the principlesdisclosed;

FIG. 2 is a (side view) schematic representation of a ferrule holdingtool and a polisher, the ferrule holding tool including a first groupingof blank ferrules, in accordance with the principles disclosed;

FIG. 3 is a (side view) schematic representation of a blank ferruleafter being polished by the polisher of FIG. 2;

FIG. 4 is an enlarged cross-sectional representation of a portion of thepolished blank ferrule of FIG. 3;

FIG. 5 is a (side view) schematic representation of a loaded ferrulehaving optical fibers inserted within the ferrule of FIG. 3;

FIG. 6 is a (side view) schematic representation of the ferrule holdingtool of FIG. 2, the ferrule holding tool including the first grouping ofloaded ferrules and a second grouping of blank ferrules;

FIG. 7 is a (side view) schematic cross-sectional representation of thecompleted, polished ferrule assembly of FIG. 1;

FIG. 8 is an enlarged view of a portion of the completed, polishedferrule assembly of FIG. 7;

FIG. 9 is a block diagram of a method for manufacturing ferruleassemblies, in accordance with the principles disclosed; and

FIG. 10 is a (side view) schematic representation of an alternative stepof polishing the optical fibers of loaded ferrules, in accordance withthe principles disclosed.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary aspects of the presentdisclosure that are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Referring to FIG. 1, the present disclosure relates to methods ofmanufacturing a multi-fiber ferrule assembly 10 for use in a fiber opticconnector. The ferrule assembly 10 generally includes a ferrule 12configured to hold a plurality of optical fibers 14. The method involvespre-polishing blank ferrules 12 in a first polishing operation, and thenpolishing the optical fibers 14 of loaded ferrules (i.e., pre-polishedferrules that hold optical fibers) in a second polishing operation.

Referring to FIG. 2, a ferrule holding tool 20 and a polisher 30 areschematically represented. As will be understood, various types offerrule holding tools and polishers can be used in accordance with theprinciples of the methods disclosed. The ferrule holding tool 20 definesa plurality of ferrule holding locations 22. In one embodiment, theferrule holding locations 22 are defined by through bores correspondingin shape and size to the ferrules 12. Typically, the tool 20 defines tento twelve ferrule holding locations 22; however, the plurality offerrule holding locations can include a greater or lesser number offerrule holding locations.

In the illustrated ferrule representation of FIG. 2, the ferrules 12 areshown schematically from the side such that the array of optical fibers14 (shown in FIG. 1) extends into the illustration. While the presentmethod is describe with respect to ferrules configured to hold multipleoptical fibers 14, it is to be understood that the present method canalso be applied to the manufacture of ferrules configured or constructedto receive only a single optical fiber. Further, while the illustratedmulti-fiber ferrule assembly 10 (FIG. 1) is shown with twelve opticalfibers 14, it is to be understood that the disclosed method appliessimilarly to multi-fiber ferrule assemblies having a greater or lessernumber of optical fibers.

Referring then still to FIG. 2, in the present method of manufacturingferrule assemblies, a grouping or number of first ferrules 16 ispositioned within a corresponding number of ferrule holding locations22. In FIG. 2, only a partial number of the ferrule holding locations 22are shown. Typically, the number of first ferrules 16 positioned withinthe tool 20 is equal to half the number of ferrule holding locations 22.In one method, the first ferrules 16 of the grouping are positioned inalternating locations such that empty ferrule holding locations areprovided between occupied ferrule holding locations, as shown in FIG. 2.By alternating the locations of the first ferrules, pressure orpolishing forces applied by the polisher 30 are more uniformlydistributed across the grouping of first ferrules 16.

In this initial step, the first ferrules 16 are empty or blank ferrules.That is, none of the ferrules 16 have received or hold optical fibers14. With the blank first ferrules 16 positioned within the ferruleholding locations 22, a first polishing operation is performed.Referring to FIGS. 2 and 3, during the first polishing operation, afront end face 28 of each of the blank ferrules 16 is simultaneouslyground or polished.

In the illustrated method, the unpolished ferrules 12 have standard,flat end faces 28 (FIG. 2). The ferrule holding tool 20 is constructedsuch that the ferrules 12 positioned within the ferrule holdinglocations 22 are oriented at an angle A1 (FIG. 2) relative to thepolisher 30; the end faces 28 of the ferrules being polished at acorresponding angle A2 (FIG. 4). In one embodiment, the angle A2 atwhich the end faces 28 of the ferrules 12 are polished is between 5 and10 degrees; in the illustrated embodiment, the end faces 28 are polishedat an angle A2 of about 8 degrees. In an alternative polishing operationset up, the ferrules 12 may be oriented in a non-angled or verticalorientation, and the polisher 30 oriented in an angular orientation.

Referring now to FIGS. 2-4, during the first polishing operation, adepth D1 (FIG. 4) of material is removed from the flat end face(represented by dashed lines) of each of the blank ferrules 12. Thedepth D1 is defined along a centerline C1-C1 of the ferrule 12. In onemethod, the depth D1 is approximately 170 micrometers at the centerlineC1-C1 of the ferrule when the end face 28 is polished at an angle A2 ofabout 8 degrees.

After the first polishing operation, the grouping of polished, angled,blank ferrules 16 is removed from the tool 20. The optical fibers 14 arethen inserted into through bores 26 formed in the ferrules. Each of theferrules 12 and the associated optical fiber 14 are secured relative toone another, typically by an epoxy or other adhesive.

Referring now to FIG. 5, the optical fibers 14 are secured relative tothe ferrule 12 such that the optical fibers 14 extend a distance D2beyond the polished end face 28 of the ferrule. The distance D2 isdefined as the distance from the end face 28 of the ferrule to the endof the optical fiber 14 when taken along a centerline C2-C2 of theoptical fiber 14. Preferably, the distance D2 is greater than that of adesired end height H (FIG. 8) of the optical fibers of the finishedferrule assembly 10. In one method, the optical fibers 14 are cleaved toextend the distance D2 beyond the end face 28 of the ferrule. In anothermethod, the optical fibers 14 are simply positioned to extend thedistance D2 beyond the end face 28 of the ferrule 12.

With the optical fibers 14 inserted and secured within the through bores26 of the ferrules, the ferrules are no longer blank; the ferrules areinstead “loaded” ferrules. The grouping of loaded first ferrules 16 isthen again positioned in the ferrule holding locations 22 of the tool 20(see FIG. 6). Preferably, each of the loaded first ferrules 16 ispositioned in the same location 22 and orientation as that at which theferrule was initially polished during the first polishing operation. Byre-positioning the ferrules in the same location 22 of the tool 20, andin the same orientation, dimensional tolerances of each individualferrule holding location of the tool and the dimensional tolerances ofeach individual ferrule are better managed.

Referring to FIG. 6, in one variation of the present method, the nextstep of manufacturing includes positioning a second grouping or numberof blank second ferrules 18 within a corresponding number of ferruleholding locations 22, along with the grouping of loaded first ferrules16. Typically, the number of second ferrules 18 positioned within thetool 20 is equal to the remaining number of empty ferrule holdinglocations.

With both the grouping of blank second ferrules 18 and the grouping ofloaded first ferrules 16 positioned within the ferrule holding locations22 of the tool 20, a second polishing operation is performed.

In the second polishing operation, the end faces 28 of each of the blanksecond ferrules 18 is ground or polished to the angle A2, as previouslydescribed (see FIGS. 3 and 4). During this same second polishingoperation, the optical fibers 14 of the loaded first ferrules 16 arepolished simultaneously with the end faces 28 of the blank ferrules 18.Due to the angled orientation of the ferrule holding locations 22 of thetool 20, the optical fibers 14 of the grouping of loaded first ferrules16 are polished at an angle A3 (FIG. 7). As can be understood, the angleA3 of the optical fibers 14 is equivalent to the angle A2 of the endface 28 of the ferrules 12. (E.g., the angle A3 is typically between 5and 10 degrees; in the illustrated embodiment, the angle A3 is about 8degrees.)

Referring still to FIG. 6, one advantage of the present method ofmanufacturing the ferrule assemblies concerns the application ofpolishing forces generated by the polisher 30. During the secondpolishing operation, the grouping of blank second ferrules 18 providesgreater surface area on which to apply polishing forces. By this, theend height H (FIG. 8) of the optical fibers 14 can be increased.

In particular, because of the small size of optical fibers, polishingforces can rapidly remove material from the ends of the fibers. Therapid rate at which material is removed is difficult to control inconventional manufacturing processes. In the present method, the endsurfaces 28 of blank ferrules 18 reduce the rate at which material isremoved from the ends of the optical fibers 14 of the loaded ferrules;and thereby offers better control and management of the resulting heightof the optical fibers. Optical fibers 14 manufactured by the presentmethod can have a protruding end height beyond that of 3 micrometers ofconventionally manufactured assemblies. In the present method ofmanufacture, the optical fibers 14 typically have an end height H ofbetween 3 and 18 micrometers; and preferably between 5 and 18micrometers; however, the end height H can be significantly greater than18 micrometers.

In addition to reducing the rate at which material is removed from theends of the optical fibers, during the second polishing operation, thegrouping of blank second ferrules 18 can also function as an indicatorof the polishing depth or resulting end height H of the optical fibers14. That is, the amount of material removed from the blank secondferrules 18 can be monitored and used as an indicator of when theoptical fibers 14 of the loaded ferrules 16 have reached the desiredfiber height H.

In particular, the resulting height H of the optical fibers 14 of theloaded ferrules 16 can be controlled during the second polishingoperation by monitoring the amount of material removed from the end face28 of the grouping of blank second ferrules 18. The depth of materialremoved from the end face 28 of the blank ferrules 18 corresponds to theheight H of the optical fibers 14 of the loaded ferrules 16. Forexample, if the desired amount of material removed from the end faces 28of the ferrules 12 corresponds to a depth D1 of 170 micrometers, thenpolishing the grouping of second blank ferrules 18 to remove an amountof material corresponding to a distance of 160 micrometers results in anoptical fiber 14 having an end height H of 10 micrometers. During thesecond polishing operation, the height H of the optical fiber can beinspected and measured for verification.

As can be understood, the second polishing operation is stopped prior topolishing the blank second ferrules 18 to the desired depth D1. That is,the grouping of blank second ferrules 18 is only partly ground orpolished in this second polishing operation. As described above, forexample, the blank second ferrules 18 are polished to remove a depth ofmaterial of approximately 170 micrometers in the second polishingoperation; the optical fibers 14 of the loaded ferrules 16 reaching thedesired fiber height H of approximately 10 micrometers above the endface 28 of the ferrule.

After the optical fibers 14 have been polished to the desired fiberheight H, the grouping of first ferrules 16, now completed ferruleassemblies 10 (FIG. 7), is removed from the tool 20. The secondpolishing operation is then completed by polishing the grouping of blanksecond ferrules 18 to the desired depth D1; for example, the blanksecond ferrules 18 are further polished to remove approximately 10micrometers of addition material from the end faces 28.

Referring now to FIG. 9, in general, the present method includespositioning the first grouping of blank ferrules 16 within the ferruleholding tool 20. The first grouping of blank ferrules 16 is ground orpolished. The optical fibers 14 are then inserted within the polishedferrules and secured in position such that the fibers 14 extend adistance beyond the polished end of the ferrules. The grouping of loadedfirst ferrules 16 and the second grouping of blank ferrules 18 are thenpositioned within the ferrule holding tool 20. The polisher 30simultaneously polishes both the blank second ferrules 18 and theoptical fibers 14 of the loaded ferrules 16. Once the desired resultingheight H of the optical fibers 14 is achieved, the polished loadedferrules 16 (i.e., the ferrule assemblies 10) are removed from the tool.The second polishing operation is then completed by finishing thepolishing of the grouping of blank second ferrules 18.

After completion of the second polishing operation, the second blankferrules 18 of the second grouping are loaded, i.e., optical fibers 14are secured within the through bore 26 of the ferrules. The loadedferrules are then re-positioned within the locations 22 of the tool 20,and a new grouping of blank ferrules is positioned with the remaininglocations of the tool. The polisher 30 then polishes both the new blankferrules and the optical fibers 14 of the second grouping of loadedferrules 18. As can be understood, ferrules can be continuously cycledthrough both of the first and second polishing operations, as describedabove, resulting in groupings of completed, polished ferrule assemblies10.

Referring now to FIG. 10, in another variation of the present method,the first polishing operation includes pre-polishing a grouping of blankferrules, as previously described and shown in FIG. 2. In this methodvariation, however, the number of blank ferrules of the grouping 116(FIG. 10) can be equal to the number of ferrule holding locations 22.That is, the entire tool 20 can be populated with blank ferrules, asopposed to being only partly populated as previously described. Afterpre-polishing the grouping 116 of blank ferrules 12, optical fibers aresecured within the through bores 26 of the pre-polished ferrules; theloaded ferrules then re-positioned within the tool 20.

In the second step of polishing the optical fibers, a spacer 40 is usedto monitoring or controlling the desired end height H of the opticalfibers 14. In the illustrated embodiment, the spacer 40 is disposed onthe tool 20. The spacer 40 has a H1 corresponding to the desired endheight H of the optical fibers 14. In this method variation, the desiredend height H (represented by a dashed line) of the optical fibers 14 ofthe loaded ferrules 16 is controlled during the second polishingoperation by monitoring when the polisher 30 contacts the spacer 40.

In one embodiment, the spacer 40 can be an amount of glue deposited onthe tool 20 prior to each of the second polishing operations. Multipleglue spacers 40 can be deposited on the tool 20 at spaced apartlocations. A tube 42, for example, can be used to construct or providethe spacer 40. In using a tube, a predetermined amount of gluecorresponding to the height H1 is administered into the tube 42 andpermitted to dry. The tube 42 can have a height H3 such that the tube 42is filled to the top to provide a spacer having the height H1.Alternatively, the tube 42 can have indicia corresponding to theparticular height H1 of the spacer 40. Yet in another alternative, aquick-drying predetermined amount of material can be deposited onto thetool without use of a set-up tube.

In this second method variation, the optical fibers 14 are polished tothe desired fiber height H; the spacer providing the indication of whenthe optical fibers have reached the desired fiber height. The height Hof the optical fiber can be inspected and measured during this secondpolishing operation for verification. After reaching the desired height,the completed ferrule assemblies 10 are removed from the tool 20 and anew grouping of blank ferrules positioned within the tool formanufacture.

The present method of manufacturing a ferrule assembly 10, including thevariations described, is accomplished without removing material from theferrule 12 after the optical fiber 14 has been secured to the ferrule.Instead, this method polishes only the optical fiber to the desiredheight, as opposed to removing material from the end face 28 of theassociated ferrule to achieve the desired height. The additional blankferrules, or spacer, aid in reducing the rate at which material isremoved from the optical fiber, providing better control over theresulting optical fiber height. By controlling the fiber polishingprocess in the disclosed manner, the optical fibers of the assembliescan be manufactured with significantly increased heights, which providebetter contact and connectivity between fiber optic connectors.

In the present method, there is also no requirement for special orcustom-made ferrules having bumps or spacer structure that control thepolished fiber height. Instead, the present method is cost-effective inthat standard flat-surfaced ferrules can be utilized for the manufactureof angled ferrule assemblies.

The above specification provides a complete description of the presentinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, certain aspects ofthe invention reside in the claims hereinafter appended.

1. A method of manufacturing a ferrule assembly, comprising the stepsof: a) providing a ferrule holding tool, the tool defining a pluralityof ferrule holding locations; b) positioning a blank ferrule at one ofthe ferrule holding locations; c) performing a first polishing operationwherein an end of the blank ferrule is polished; d) securing thepolished ferrule to an optical fiber such that the optical fiber extendsa distance beyond the polished end of the ferrule; and e) performing asecond polishing operation wherein an end of the optical fiber ispolished without removing material from the polished end of the ferrule.2. The method of claim 1, wherein the step of positioning the blankferrule includes positioning the blank ferrule at an angle within thetool such that the polished blank ferrule has an angled polished end. 3.The method of claim 1, wherein the step of performing the firstpolishing operation includes polishing the end of the blank ferrule atan angle.
 4. The method of claim 3, wherein the step of polishing theend of the blank ferrule includes polishing the end of the blank ferruleat an angle of about 8 degrees.
 5. The method of claim 1, wherein thestep of performing the second polishing operation includes polishing theend of the optical fiber to a height of greater than 3 micrometers. 6.The method of claim 5, wherein the step of polishing the end of theoptical fiber includes polishing the end of the optical fiber to heightof between 5 and 18 micrometers.
 7. The method of claim 1, wherein thestep of performing the second polishing operation includes positioningthe polished ferrule having the optical fiber in the same holdinglocation as that at which the ferrule was positioned during the firstpolishing operation.
 8. The method of claim 1, wherein the step ofperforming the second polishing operation includes positioning a blanksecond ferrule at another one of the ferrule holding locations, andpolishing an end of the blank second ferrule simultaneously with the endof the optical fiber.
 9. The method of claim 8, wherein the step ofpolishing the end of the blank second ferrule includes removing a depthof material from the end of the blank second ferrule, the depthproviding an indication of when the optical fiber has reached a desiredfiber height.
 10. The method of claim 8, further including reducing therate at which material is removed from the end of the optical fiber bysimultaneously removing material from the end of the blank secondferrule.
 11. The method of claim 1, further including positioning anumber of blank ferrules at the ferrule holding locations of the tool,the number of blank ferrules corresponding to approximately one-half thenumber of ferrule holding locations.
 12. The method of claim 11, furtherincluding positioning the number of blank ferrules in alternatingferrule holding locations such that empty ferrule holding locations areprovided between occupied ferrule holding locations.
 13. The method ofclaim 1, further including providing a spacer on the ferrule holdingtool, the spacer having a spacer height corresponding to a desired fiberheight, the spacer providing an indication of when the polished opticalfiber has reached the desired fiber height.
 14. The method of claim 13,further including providing a polisher and monitoring when the polishercontacts the spacer as an indication of when the polished optical fiberhas reached the desired fiber height.
 15. The method of claim 1, furtherincluding positioning a number of blank ferrules at the ferrule holdinglocations of the tool, the number of blank ferrules generallycorresponding to the number of ferrule holding locations.